This invention relates to drain devices and refers more particularly to a drain assembly for use with a pressurized compartment such as found in aircraft and like vehicles operating at high altitude levels.
Liquids can accumulate for various reasons in the cabin space of aircraft type vehicles. For example, liquid spill of beverages can occur where a pilot or passenger is taken unaware by a sudden change in aircraft altitude. In small aircraft such as a military fighter plane, relief tube body waste discharge can be present in the cabin space. In addition, a military aircraft sitting at a maintenance site can have its cockpit cover open when a sudden downpour of rain occurs and a quantity of rainwater enters the cockpit before a mechanic can close the cover. For this reason, it is desirable that overboard drainage be provided so that liquid accumulation readily and conveniently can be discharged from the cabin to the extra vehicle environment. However, the drainage capability must be provided in such manner as takes into account the requirement for maintaining pressurized condition in the cabin when the aircraft is operating at certain altitude levels. Depending on altitude, cabin pressures can vary over a range from 0 to about 10 psig. Accordingly, any devices employed for drainage purposes must not allow for the possibility that cabin depressurization could occur through the drainage device at least where cabin pressures above a certain magnitude are involved. At the same time, the drainage device should be operable to allow for drainage at pressures below this certain magnitude so that cabin liquid accumulation which commonly may be of corrosive nature, is a hazard to electrical devices as well as being malodorous, can be discharged overboard from the aircraft.